Philosophically speaking, evil does not exist. God is good, and all that God created is good. Nothing exists except God and all that God created. So then, what is evil? Evil is a deprivation of goodness; it is an absence of goodness contrary to the plan of God the Creator. So when a fallen angel chooses to do evil, his own good nature, as created by God, is a witness against his choice of evil acts. And when a human person chooses to do evil, his own good nature, as created by God, is a witness against his choice of evil acts.
An act is evil due to a deprivation of moral goodness. This moral goodness or its absence, in any act, is determined by the eternal moral law, by the Justice inherent in the very Nature of God. But the eternal moral law is the law of love: the love of God above all else and the love of neighbor as self. So an act is evil when it has a deprivation of the properly-ordered love of God, neighbor, self. Any act contrary to that love is a sinful act.
More specifically, an act is good or evil based on the knowing choices of the human person. The will chooses a particular type of act, with a particular intention, within a set of circumstances with knowledge of the possible consequences. The type of the act, in terms of morality, is determined by the moral object, the end toward which the act itself is inherently ordered. Each and every knowing choice of the human person has three sources or ‘fonts’ of morality: intention, moral object, circumstances. In order to be moral, each knowingly chosen act must have three good fonts:
1. only good intention(s)
2. only good moral object(s)
3. and any reasonably anticipated bad consequences must not outweigh the reasonably anticipated good consequences
Each font is judged to be good or bad based on the love of God, neighbor, self. One or more bad fonts makes any act a sin.
If the moral object of any act is evil, that is to say, if it is contrary to the love of God and the love of neighbor as self, then that act is intrinsically evil. Such an act is immoral by its very nature. Therefore, every intrinsically evil act is always immoral, regardless of intention or circumstances.
An act can have more than one moral object, in which case all the moral objects might be good, or all might be bad, or some might be good while others are bad. Even a single bad moral object makes the act intrinsically evil and always immoral.
For example, simple theft has an evil moral object, to deprive your neighbor of his rightful property. But suppose that someone were to steal a sacred object, such as a gold vessel used in the Mass. This one act would then have two evil moral objects, that of sacrilege as well as that of theft. So nothing prevents an act from having more than one moral object.
Intrinsically Evil Sexual Acts
Any sexual act with one or more bad moral objects is an intrinsically evil act. And since intrinsically evil sexual acts offend against goods of high moral value (human sexuality and procreation), an intrinsically evil sexual act is always gravely immoral.
The good moral object of any moral sexual act is threefold: marital, unitive, and procreative. We can consider this to be one moral object with three components (as God is one yet three). Or we can simply consider them to be three separate but interrelated moral objects. In any case, all moral objects must be good for any sexual act to be inherently good, rather than inherently evil.
The marital meaning is only present when the natural sexual act occurs between a man and a woman married to each other. Any knowingly chosen sexual act that is deprived of the marital meaning is intrinsically evil and always gravely immoral.
“May marriage be honorable in every way, and may the marriage bed be immaculate. For God will judge fornicators and adulterers.” (Hebrews 13:4)
Masturbation is deprived of the marital meaning, therefore it is intrinsically evil and always gravely immoral. Even if the person who commits this sin is married, this solitary act is non-marital.
If one spouse commits this type of act on the other spouse (masturbation of another person, also called manipulative sex), the act is nevertheless non-marital. For this is not the type of sexual act that God intends for marriage. This is not the type of sexual act that consummates a marriage and is a continuing part of the Sacrament of Marriage. Every type of masturbation is intrinsically evil and always gravely immoral because it is non-marital. This type of sexual act is also non-unitive and non-procreative; so it has three evil moral objects, and is therefore particularly disordered.
Premarital sex is deprived of the marital meaning, and therefore is intrinsically evil and always gravely immoral. Even if the couple are engaged and have every intention of marrying soon, they are not yet married in the eyes of God and of His Church, and so they do not have the marital meaning. All premarital sex has the evil moral object of the deprivation of the marital meaning. God wills that the expression of human sexuality in sexual acts occur only within marriage.
Adultery is more gravely disordered than premarital sex, because adultery has two evil moral objects: the deprivation of the marital meaning, and the breaking of the marital vow. In addition, there are generally more bad consequences in the third font of morality for adultery than for premarital sex, and this increases the immorality of the act when all the fonts are considered.
This moral object of the sexual act is often misrepresented. It is not mere physical union. A handshake or a hug has a mere physical union, but not the unitive meaning. Unnatural sexual acts, such as homosexual sex, have a certain physical union, but they do not have the unitive meaning. Neither is the unitive meaning equivalent to sexual pleasure, nor shared sexual pleasure. None of these things are the unitive meaning.
The unitive meaning is a specific type of physical union, the sexual union of a man and a woman in natural intercourse. This type of sexual act is in harmony with, and ordered toward, the other meanings: marital and procreative.
“Canon 1061 §1. A valid marriage between the baptized is called ratum tantum if it has not been consummated; it is called ratum et consummatum if the spouses have performed between themselves in a human fashion a conjugal act which is suitable in itself for the procreation of offspring, to which marriage is ordered by its nature and by which the spouses become one flesh.”
All three meanings, found in the proper moral object of every moral sexual act, are interrelated. The unitive meaning is ordered toward the marital meaning. In fact, this union is necessary for the consummation of the marriage. And the unitive meaning is ordered toward the procreative meaning. For the type of act must be open to life. If injury, or illness, or old age make procreation unlikely or impossible, the type of act must nevertheless be ordered toward procreation. It is not the attainment of the moral object that makes an act moral or immoral, but rather the inherent ordering of the act toward that moral object.
So the unitive meaning is found only in natural intercourse between a man and a woman, in the type of act that is inherently ordered toward procreation. No other sexual act, even between spouses, has this unitive meaning. And therefore, all other types of sexual acts (such as oral sex, anal sex, manipulative sex) are non-unitive and therefore intrinsically evil, even between spouses.
Since intrinsically evil acts are always immoral, regardless of intention or circumstances, no purpose or intention, and no circumstance however dire, can justify unnatural sexual acts, even within marriage. The intention to use an unnatural sexual act as foreplay, to prepare for the natural act, does not justify that intrinsically evil unnatural sexual act. The circumstance that the wife cannot reach climax without an unnatural sexual act does not justify that intrinsically evil unnatural sexual act. (See also: Unnatural sexual acts as marital foreplay)
“But no reason, however grave, may be put forward by which anything intrinsically against nature may become conformable to nature and morally good.” (Pope Pius XI, Casti Connubii, n. 54)
“No circumstance, no purpose, no law whatsoever can ever make licit an act which is intrinsically illicit. Certain negative precepts of the natural law are universally valid. They oblige each and every individual, always and in every circumstance. It is a matter of prohibitions which forbid a given action always and in each instance, without exception. It is prohibited — to everyone and in every case — to violate these precepts. They oblige everyone, regardless of the cost.” (Pope John Paul II, Veritatis Splendor, n. 52)
The procreative meaning is found only in natural intercourse. This type of sexual act is inherently ordered toward the creation of new human life. Even if each natural sexual act does not produce new life, its ordering toward new life is necessary in order to have the good moral object of the procreative meaning. Every sexual act that is not ordered toward procreation is an intrinsically evil act, including: masturbation, unnatural sexual acts (even within marriage), and homosexual acts. Neither is it sufficient for one act in a set of acts to be procreative:
“The Church, nevertheless, in urging men to the observance of the precepts of the natural law, which it interprets by its constant doctrine, teaches that each and every marital act must of necessity retain its intrinsic relationship to the procreation of human life.” (Humanae Vitae, n. 11)
In Catholic moral teaching, each and every knowingly chosen act is subject to the eternal moral law. It is never the case that one act in a set can be used to justify other acts. Each knowingly chosen act must have three good fonts, as each of those fonts arises from, and applies to, each particular act. So in the area of sexuality, each and every sexual act must be marital, unitive, and procreative. A non-procreative sexual act cannot be justified by reference to a prior, concurrent, or subsequent procreative sexual act.
However, it is the inherent ordering of an act toward the moral object of procreation that makes the act procreative, not the attainment of that end. Consider two examples:
1. A married couple use contraception, but the contraception fails and they conceive a child. The contracepted sexual act was not ordered toward the procreative meaning. Instead, the act was ordered toward an evil moral object, the deprivation of the procreative meaning. The fact that the act failed to achieve its evil end, depriving the sexual act of procreation, does not make the act moral.
2. A married couple have natural marital relations open to life, but they are infertile due to injury, illness, or old age. The type of act is inherently ordered toward the good end of procreation. The fact that the act does not, or cannot, attain that good end does not make the act immoral. Natural marital relations is ordered toward the marital, unitive, and procreative meanings by its very nature.
It is the intrinsic ordering of an act toward good or evil moral objects that makes the act intrinsically good or intrinsically evil — not the attainment of that moral object.
Although the various forms of artificial procreation (e.g. IVF, cloning) result in the creation of a new human life, the procreative meaning is harmed by the disordered means of procreation, and the unitive meaning is absent. Neither can artificial procreation be considered truly marital, even if the source of the gametes is a husband and wife, because this is not the type of procreation intended by God for marriage.
Marital, Unitive, Procreative
Every sexual act that is marital, unitive, and procreative is an inherently good type of sexual act. However, the other two fonts of morality — intention and circumstances — must also be good for the couple to avoid sin.
Every sexual act that is non-marital, or non-unitive, or non-procreative is intrinsically evil and always gravely immoral. Nothing can justify an intrinsically evil act. It is the type of act that is inherently contrary to the love of God, neighbor, and self.